1. Field of the Invention
The present invention relates to a medium storing a print density correction program which corrects the print density on the basis of variations in ink density, an apparatus and method for the correction of print density, a medium which stores a print control program, and an apparatus and method for print control.
2. Description of the Prior Art
In a conventional ink jet printer which makes printing by ejecting ink onto a recording medium such as paper, the amount of ink is kept constant when printing is made at a predetermined print density irrespective of a residual amount of ink.
In the above conventional ink jet printer, particularly when using a pigment-based ink, the print density changes with time, depending on a residual amount of ink, with consequent variations in ink density. That is, the ink density is low in an upper layer within an ink cartridge filled with ink and becomes higher gradually toward a lower layer. In printing, ink is used successively from the lower layer of a high ink density. Therefore, as the amount of ink becomes small, the ink density becomes low and so does the print density gradually.
The present invention has been accomplished in view of the above-mentioned problem and it is an object of the invention to provide a medium storing a print density correction program which corrects the print density on the basis of variations with time in ink density to permit printing at a constant print density, an apparatus and method for the correction of print density, a medium which stores a print control program, and an apparatus and method for print control.
In the medium which stores a print density correcting program according to the present invention, the program causes a computer to correct variations in print density based on variations in ink density and corresponding to changes with time in ink density in a printer which makes printing by ejecting ink onto a printing medium. In accordance with the print density correcting program the computer is allowed to execute an identification information acquiring function of acquiring identification information which permits the degree of variations in ink density to be identified directly or indirectly, as well as a print density correcting function comprising acquiring a correction coefficient for correcting variations in print density corresponding to changes with time in ink density and correcting the print density so as to eliminate the variations in print density in accordance with the acquired correction coefficient.
In the present invention thus constructed, the computer executes the identification information acquiring function, that is, acquires identification information which permits the degree of variations in ink density to be identified directly or indirectly in a printer, the printer ejecting ink onto a printing medium to effect printing, then the computer executes the print density correcting function, that is, acquires a correction coefficient for correcting the variations in print density corresponding to the changes with time in ink density in accordance with the identification information acquired, and thereafter corrects the print density so as to eliminate the variations in print density on the basis of the correction coefficient thus acquired.
Usually, when printing is performed on the basis of a predetermined print density, there is made control so that a predetermined amount of ink which can realize the said print density is ejected onto a printing medium. However, if there are variations in the density of the ink ejected, even if the ink is ejected in the predetermined amount onto the printing medium, there will occur variations in the actual print density which is expressed by the said amount of ink. In the present invention, when printing is performed, the print density is corrected while taking such variations in ink density into account so that the actual print density becomes a desired print density.
Therefore, according to the present invention it is possible to provide a medium storing a print density correcting program which corrects the print density on the basis of variations in ink density, thereby permitting printing to be carried out at a certain constant print density even with the lapse of time.
In executing the identification information acquiring function, that is, when acquiring identification information which permits the degree of variations in ink density to be identified, a state of ink may be acquired directly and used as the identification information, or there may be acquired identification information which can identify the degree of variations in ink density indirectly. In executing the identification information acquiring function, the timing for acquiring the same information is not specially limited. The identification information may be acquired when printing is started, or it may be acquired during printing. The print density correcting function may be carried out so as to correct the print density in accordance with the identification information thus acquired.
As to the identification information acquired by the identification information acquiring function, no special limitation is placed on whether it is to be acquired directly or indirectly insofar as it can identify the degree of variations in ink density as noted above.
As an example of identification information able to identify the degree of variations in ink density, there may be adopted a construction wherein information on the amount of ink used is acquired as the identification information in the identification information acquiring function and a correction coefficient based on a correlation between the information on the amount of ink used and information on changes in print density is acquired in the print density correcting function.
According to this construction, information on the amount of ink used is acquired as the identification information by the identification information acquiring function, so in the print density correcting function there is acquired a correction coefficient based on a correlation between the information on the amount of ink used and information on changes in print density. The information on the amount of ink used, which is acquired by the identification information acquiring function, may be one managed by a printer connected to an apparatus which implements the same function or may be one managed by a print controller which controls the printer. It may be changed as necessary. As to the amount of ink used, an actual amount of ink used may be measured and used as the information on the amount of ink used, or a residual amount of ink may be measured to determine the amount of ink used indirectly and the amount of ink thus determined may be used as the information on the amount of ink used, or the amount of ink used may be determined on the basis of the number of printed sheets and used as the information on the amount of ink used. Thus, a change maybe made as necessary. The degree of variations in ink density depends on changes with time after charging the ink into an ink cartridge or the like, so by utilizing the information on the amount of ink used it becomes possible to identify such changes with time, i.e., the degree of variations in ink density.
This permits the correction of the print density in accordance with the information on the amount of ink used.
As noted above, the degree of variations in ink density depends on changes with time after the ink has been charged into an ink cartridge or the like. As another example of identification information able to identify the degree of variations in ink density based on such changes with time in ink density, there may be adopted a construction wherein information on the manufacture of ink is acquired as the identification information in the identification information acquiring function, while in the print density correcting function there is acquired a correction coefficient based on a correlation between elapsed time after the manufacture of ink based on the said information on manufacture and information on changes in print density.
In the above construction, information on the manufacture of ink is acquired as identification information by the identification information acquiring function, so in the print density correcting function there is acquired a correction coefficient based on a correlation between elapsed time after the manufacture of ink based on the said information on manufacture and information on changes in print density. The information on the manufacture of ink specifies when ink was manufactured in a state employable for printing such as a filled state into an ink cartridge or the like. It may be the date or time of manufacture. The information on the manufacture of ink may be recorded on an ink cartridge or the like simultaneously with the manufacture of ink in such a manner that it can be read from the exterior by the identification information acquiring function.
This permits the correction of the print density in accordance with the information on the manufacture of ink.
Needless to say, both may be combined together. In this case, in the identification information function there is acquired as the identification information both information on the amount of ink used and information on the manufacture of ink, while in the print density correcting function there is acquired a correction coefficient which reflects information on changes in print density based on both information on the amount of ink used and information on the manufacture of ink.
It is as noted above that changes with time in ink density can be recognized from both information on the amount of ink used and information on the manufacture of ink. In some case, after ink being filled into an ink cartridge or the like until actual use thereof the ink is managed so as to prevent the occurrence of variations in ink density. In such a case, it is preferable if changes with time in ink density can be identified after the ink has become actually employable in printing. In this connection there may be adopted a construction wherein in the identification information acquiring function there is acquired information on the replacement of ink as the identification information, while in the print density correcting function there is acquired a correction coefficient based on a correlation between changes with time in ink density based on the ink replacement information and changes in print density.
In this construction, information on the replacement of ink is acquired by the identification information acquiring function, so in the print density correcting function there is acquired a correction coefficient based on a correlation between changes with time in ink density based on the ink replacement information and changes in print density. The ink replacement information specifies when ink was filled into an ink cartridge or the like and became employable for printing with the cartridge loaded into a printer. It may be the date or time of ink replacement. It is optional whether the ink replacement information is to be managed on the printer side and is read by the identification information acquiring function or is managed on a print controller side and is read by the identification information acquiring function.
This permits the correction of the ink density on the basis of ink replacement information.
As an example of construction wherein the print density is corrected by the print density correcting function on the basis of the identification information acquired by the identification information acquiring function, there may be adopted a construction wherein in the print density correcting function the print density is corrected in the course of conversion to color data of a color space different from color data of a predetermined color space in print control.
For example, color data on a computer often utilizes RGB space as a color space, while in a printer or the like CMY space is often utilized. Therefore, color data is converted from RGB data to CMY (or CMYK) data. Print density is corrected in the course of this conversion.
In this case, as a more concrete construction there may be adopted a construction wherein in the print density correcting function data in a color conversion table, which is referred to in the course of the above conversion to color data, are rewritten to correct the print density.
According to this construction, by rewriting data in the color conversion table on the basis of the identification information acquired, the print density is corrected by mere reference to the color conversion table even without repeating the correction of print density for each individual case. The color conversion table is a data table for converting predetermined element colors which represent constituent picture elements of an image into deep/thin element colors.
As described above, the predetermined element colors which represent the constituent picture elements of an image are converted to deep/thin element colors by the color conversion table. Since printing is performed on the basis of the thus-converted deep/thin element colors, the print density can be corrected by rewriting the data of the color conversion table in accordance with the identification information. The timing for modifying the color conversion table is not specially limited, but may be based on the timing at which the identification information is acquired. Therefore, if identification information is acquired at the start of printing, the color conversion table may be modified when printing is started, and at every acquisition of identification information during printing the color conversion table may be modified accordingly.
As another concrete construction for correcting the print density in the course of color data conversion there may be adopted a construction wherein in the print density correcting function the color data after the color space conversion is converted to correct the print density.
In this construction, after color conversion made by using the color conversion table or the like, the print density based on the color data after the conversion is corrected for example in a state of CMY data.
For example, a conversion table in which input and output data are correlated with each other for each color may be constructed and the conversion of data may be performed by reference to the conversion table.
In the identification information acquiring function, identification information is acquired on the basis of a predetermined appropriate timing. This timing is not specially limited, but may be changed as necessary. As an example of the identification information acquiring timing in the identification information acquiring function there may be adopted a construction wherein in the identification information acquiring function the identification information is acquired at every printing of a predetermined area of an image, while in the print density correcting function the print density is corrected as necessary upon acquisition of the identification information.
According to this construction, identification information is acquired by the identification information acquiring function at a timing of printing a predetermined area of an image, then in the print density correcting function the print density is corrected as necessary at the acquired timing of the identification information.
This permits the correction of the print density for each predetermined area to be printed.
Thus, it suffices for the identification information acquiring function to acquire identification information at a timing at which the printing of a predetermined area is carried out. The predetermined area can be changed as necessary. As an example of the predetermined area there may be adopted a construction wherein in the identification information acquiring function the identification information is acquired for each printing band width, while in the print density correcting function the print density is corrected for each band width upon acquisition of the identification information.
According to this construction, identification information is acquired by the identification information acquiring function for each band width as a unit of print execution, then in the print density correcting function the print density is corrected for each band width on the basis of the identification information thus acquired. In printing, an image is divided into plural band widths and printing data are produced for each of the band widths.
Therefore, if the correction of print density is performed for each band width, it becomes possible to effect the correction of print density synchronously with printing process. Thus, it becomes possible to prevent the exertion of influence on the printing speed even while making the correction of print density plural times in printing a single image.
As another example of the predetermined area there may be adopted a construction wherein in the identification information acquiring function the identification information is acquired for each picture element to be printed, while in the print density correcting function the print density is corrected for each picture element upon acquisition of the identification information.
According to this construction, identification information is acquired by the identification information acquiring function at a timing at which each picture element is printed. In the print density correcting function, the print density is corrected for each picture element at a timing at which the identification information is acquired. By thus acquiring identification information for each picture element it becomes possible to correct the print density in real time against the degree of variations in ink density which varies with the lapse of time. Particularly, in large-sized printing, there is a large timing lag from the printing of an initial picture element until printing of a last picture element. Therefore, if the print density is corrected for each picture element, the print density can be made uniform without being influenced by variations in ink density which occur during the period between the start of printing and the end of printing.
This permits the correction of the print density in real time against the degree of variations in ink density which varies with the lapse of time.
In printing, plural inks are usually employed. Therefore, if identification information is acquired for all of the inks and if the print density is corrected on the basis of the identification information thus acquired, the processing speed in the whole of printing process may be decreased. In view of this point there may be adopted a construction wherein in the print density correcting function the correction of print density is not performed for a predetermined element color.
According to this construction, since the correction of print density is not performed for a predetermined element color in the print density correcting function, it is not required to acquire identification information on the element color not to be corrected. By thus omitting the correction of print density for a predetermined element color it becomes possible to improve the processing speed in printing process.
As an example of such omission of the element color correction, the correction of print density may be omitted for yellow color.
As an example of a basic condition in the selection of ink for which the correction of print density is not performed, there may be adopted a construction wherein in the print density correcting function the correction of print density is not performed for a relatively thin element color out of plural element colors.
Thus, as to ink which is utilized for printing a relatively thin element color, variations in ink density are connived and the correction of print density is not performed, whereby it becomes possible to increase the processing speed in printing process.
More particularly, as to ink which is utilized for printing a thin element color, even if there occur a certain degree of variations in ink density with consequent occurrence of variations in print density, it is difficult for a human to visually confirm such variations in print density on a thus-printed matter. Besides, a printed matter is usually composed of plural element colors, so in the case of a relatively thin color, variations in print density become less conspicuous in comparison with the other colors. For this reason, as to the ink which is utilized for printing a relatively thin element color, variations in ink density are connived and the correction of print density is not performed, whereby it becomes possible to effect the printing process at a high speed.
As another example of a basic condition in the selection of ink not to be corrected for print density, there may be adopted a construction wherein in the print density correcting function the correction of print density is not performed for an element color of relatively small variations in ink density.
According to this construction, the correction of print density is not made for an element color of relatively small variations in ink density. The degree of variations in ink density differs for each ink color. Therefore, the correction of ink density is performed for an ink which is likely to cause a large degree of variations in ink density, while the correction of ink density is not performed for an ink which is difficult to cause variations in ink density and which is small in the degree of the variations.
Thus, as to an element color small in the degree of variations in ink density, the correction of print density is not conducted, whereby it becomes possible to speed up the printing process.
A printed matter usually comprises plural element colors, and in the case of an element color relatively small in the degree of variations in ink density, variations in print density are less conspicuous in comparison with the other element colors. Therefore, as to an ink which is utilized for an element color relatively small in the degree of variations in ink density, the variations in ink density are connived and the correction of print density is not performed, whereby the printing process can be carried out at a high speed.
As an example of ink which can cause variations in ink density there is mentioned an aqueous pigment ink.
Such an aqueous pigment is insoluble in water and it is necessary to prepare an ink in the form an aqueous dispersion with pigment particles dispersed in water. In such a pigment ink as an aqueous dispersion, the pigment particles contained in the dispersion precipitate with the lapse of time and there occurs a gradient in the concentration of pigment particles contained in the ink dispersion. That is, variations in ink density occur.
Thus, it is more preferable to apply the present invention to ink constituted by an aqueous pigment having such a characteristic.
Consequently, it is possible to correct variations in print density caused by variations in ink density and present a preferred example of ink.
The print density correcting program described above may be executed alone, but may also be implemented as one function of a printer driver for print control. More specifically, according to the present invention there is provided a medium with a print density correcting program stored thereon, the program being adapted to operate on a computer to correct variations in print density in a printer based on variations in ink density which correspond to changes with time in ink density, the computer capable of being connected to the printer which makes printing by ejecting ink onto a printing medium and being provided with an interface which can transmit data. In accordance with the print density correcting program, an identification information acquiring function of acquiring identification information which permits the degree of variations in ink density to be identified directly or indirectly, and a print density correcting function comprising acquiring a correction coefficient and correcting the print density so as to eliminate the variations in print density in accordance with the correction coefficient acquired, the correction coefficient being for correcting variations in print density corresponding to changes with time in ink density in accordance with the identification information acquired, are executed by the computer.
In this sense the printer driver itself may be applied. In this case, according to the present invention there is provided a medium with a print control program stored thereon, the program being adapted to operate on a computer to input image data of a color space different from a color space of printing data capable of being printed in a printer and convert the image data into printing data which the printer can print and then output the thus-converted printing data, the computer capable of being connected to the printer which makes printing by ejecting ink onto a printing medium and being provided with an interface which can transmit data. In accordance with the print control program, a conversion function of converting the image data into the printing data, an identification information acquiring function of acquiring identification information which permits the degree of variations in ink density to be identified directly or indirectly, thereby correcting variations in print density based on the variations in ink density which correspond to changes with time in ink density, and a print density correcting function comprising acquiring a correction coefficient for correcting variations in print density corresponding to the changes with time in ink density in accordance with the acquired identification information, correcting the print density so as to eliminate the variations in print density on the basis of the correction coefficient acquired, and causing the thus-corrected print density to be reflected in the print data, are executed by the computer.
The recording medium described above may be a magnetic recording medium or a magneto-optic recording medium or any of recording mediums which will be developed in future.
Complete equivalence is applied to duplicating stages, including primary and secondary duplicates. Even in a combined configuration implemented by a partial software configuration and a partial hardware configuration, the idea of the present invention is applied thereto without any difference. There may be adopted a mode in which the program is partially stored on the recording medium and is read as necessary.
It goes without saying that the medium with such a print density correcting program stored thereon can alone be an object of business and also can be an object of business as a substantial apparatus constituted by means which can execute the functions implemented by the medium with the print density correcting program stored thereon. Thus, the medium with the print density correcting program stored thereon can be substantiated into a print density correcting apparatus which exhibits the same effect as above.
In this way it is possible to provide a print density correcting apparatus which corrects the print density on the basis of variations in ink density and which thereby can effect printing at a constant print density even with the lapse of time.
Further, it should be readily clear that the technique for correcting variations in print density based on variations in ink density is not always limited to a substantial print density correcting apparatus, but that even a method thereof can fulfill the function to a satisfactory extent. That is, according to the present invention it is also possible to provide a method for implementing the above print density correcting apparatus. Thus, a limitation is not always made to the substantial print density correcting apparatus, but even the adoption of a print density correcting method is also effective equally.
In this way it is possible to provide a print density correcting method which corrects the print density on the basis of variations in ink density and which thereby permits printing to be done at a constant print density even with the lapse of time.
The invention also resides in printing data itself having such a corrected print density. More specifically, such printing data is not specially limited insofar as it is a binarized printing data for which variations in print density in a printer based on variations in ink density corresponding to changes with time in ink density have been corrected, the printer ejecting ink onto a printing medium to effect printing, and for which the print density has been corrected so as to eliminate variations in print density with use of a correction coefficient based on identification information, the identification information permitting the degree of variations in ink density to be identified directly or indirectly.
When viewed from another viewpoint, there is provided, according to the present invention, a medium with a print density correcting program stored thereon, the program functioning to correct variations in pint density based on variations in ink density. In accordance with this print density correcting program, an identification information acquiring function of acquiring identification information able to identify the degree of variations in ink density and a print density correcting function of correcting variations in print density in accordance with the acquired identification information are executed by means of a computer.
According to this construction there is provided a medium with a print density correcting program stored thereon, the program functioning to correct variations in print density based on variations in ink density and capable of being executed by a computer. In this case, the medium with the print density correcting program stored thereon is constructed so as to possess both identification information acquiring function and print density correcting function. In the former function there is acquired identification information which can identify the degree of variations in ink density, while in the latter function variations in print density are corrected in accordance with the identification information acquired.
Needless to say, the invention based on such a viewpoint may be a substantial apparatus or method.